Some inkjet printers employ arrays of printheads that are mounted to print bars in a print zone. Each print bar is a rigid, elongated member that is, for example, formed from steel or another metallic structure with attachment points for one or more printheads. In one printer configuration that is known to the art, a single printhead array is formed using seven printheads that are affixed to predetermined locations on two different print bars (three printheads on a first bar and four printheads on a second bar) in a staggered configuration to enable the printheads to cover the width of the print zone. Alternative configurations use different numbers of print bars and printheads. Some inkjet printers include multiple sets of these printhead arrays to form color printed images using different printhead arrays for each color or to increase the effective resolution of the printer by interleaving lower resolution printheads in two or more printhead arrays to form printed images with a higher effective resolution.
During a printing operation the print bars should hold the printheads in fixed positions within a print zone at precise positions and orientations relative to a print medium or other image receiving member to ensure that the printheads are properly aligned to form printed images. Even comparatively small errors in the position or orientation of the printheads on the print bar may result in an easily noticeable degradation in the quality of printed images. However, while print bars remain in a fixed position during a printing operation, during printhead maintenance and other operations, a member in the print zone that carries a print medium or other image receiving surface moves away from the print bars to enable a printhead maintenance unit to clean the printheads and to provide access for printhead repair or replacement. When the unit of the printer that carries the print medium or other image receiving surface returns to engage the print bars, one or more docking pins in the unit engage a fixed bushing that is formed on at least one side of the print bar to return the components in the printer to a precise location relative to one another for additional printing in an operation that is referred to as “docking.”
Existing docking devices have drawbacks because they must both include sufficient mechanical tolerances to enable docking but also ensure that, in the docked configuration, the print bar and the unit in the printer remain at a precise position and angular orientation to ensure that the printheads on the print bar are properly aligned in the print zone to form printed images. FIG. 7 depicts challenges with a prior art locating pin 700 with a shaft 706 that is connected to a portion of a unit in the printer (not shown), such as a media control path or an indirect image receiving member that receive printed ink images from the printheads on the print bar, and an end 704 that should engage a bushing 720 that is affixed to one end of a print bar. In view 750, the end of the pin 704 is misaligned with the bushing 720 and effectively fails to engage the bushing 720. In view 760, even if the locating pin 700 engages the bushing 720, in some instances the shaft 706 deviates from a predetermined orientation (deviation from vertical in the example of FIG. 7). Even if the locating pin 700 engages the bushing 720, the print bar may still have an incorrect orientation relative to the image receiving surface that negatively impacts the quality of printed documents in the printer. Consequently, improvements to docking devices in inkjet printers that reduce or eliminate these drawbacks in prior art devices would be beneficial.